// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  linux/fs/binfmt_em86.c
   *
   *  Based on linux/fs/binfmt_script.c

   *  Copyright (C) 1996  Martin von Löwis

   *  original #!-checking implemented by tytso.
   *
   *  em86 changes Copyright (C) 1997  Jim Paradis
   */
  
  #include <linux/module.h>
  #include <linux/string.h>
  #include <linux/stat.h>

  #include <linux/binfmts.h>
  #include <linux/elf.h>
  #include <linux/init.h>
  #include <linux/fs.h>
  #include <linux/file.h>
  #include <linux/errno.h>
  
  
  #define EM86_INTERP	"/usr/bin/em86"
  #define EM86_I_NAME	"em86"

  static int load_em86(struct linux_binprm *bprm)

  {

  	const char *i_name, *i_arg;
  	char *interp;

  	struct file * file;
  	int retval;
  	struct elfhdr	elf_ex;
  
  	/* Make sure this is a Linux/Intel ELF executable... */
  	elf_ex = *((struct elfhdr *)bprm->buf);
  
  	if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
  		return  -ENOEXEC;
  
  	/* First of all, some simple consistency checks */
  	if ((elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN) ||
  		(!((elf_ex.e_machine == EM_386) || (elf_ex.e_machine == EM_486))) ||

  		!bprm->file->f_op->mmap) {

  			return -ENOEXEC;
  	}

  	/* Need to be able to load the file after exec */
  	if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
  		return -ENOENT;

  	/* Unlike in the script case, we don't have to do any hairy
  	 * parsing to find our interpreter... it's hardcoded!
  	 */
  	interp = EM86_INTERP;
  	i_name = EM86_I_NAME;
  	i_arg = NULL;		/* We reserve the right to add an arg later */
  
  	/*
  	 * Splice in (1) the interpreter's name for argv[0]
  	 *           (2) (optional) argument to interpreter
  	 *           (3) filename of emulated file (replace argv[0])
  	 *
  	 * This is done in reverse order, because of how the
  	 * user environment and arguments are stored.
  	 */
  	remove_arg_zero(bprm);

  	retval = copy_string_kernel(bprm->filename, bprm);

  	if (retval < 0) return retval; 
  	bprm->argc++;
  	if (i_arg) {

  		retval = copy_string_kernel(i_arg, bprm);

  		if (retval < 0) return retval; 
  		bprm->argc++;
  	}

  	retval = copy_string_kernel(i_name, bprm);

  	if (retval < 0)	return retval;
  	bprm->argc++;
  
  	/*
  	 * OK, now restart the process with the interpreter's inode.
  	 * Note that we use open_exec() as the name is now in kernel
  	 * space, and we don't need to copy it.
  	 */
  	file = open_exec(interp);
  	if (IS_ERR(file))
  		return PTR_ERR(file);

  	bprm->interpreter = file;
  	return 0;

  }
  
  static struct linux_binfmt em86_format = {
  	.module		= THIS_MODULE,
  	.load_binary	= load_em86,
  };
  
  static int __init init_em86_binfmt(void)
  {

  	register_binfmt(&em86_format);
  	return 0;

  }
  
  static void __exit exit_em86_binfmt(void)
  {
  	unregister_binfmt(&em86_format);
  }
  
  core_initcall(init_em86_binfmt);
  module_exit(exit_em86_binfmt);
  MODULE_LICENSE("GPL");